'[The deal] is a clear sign that Turkey is disappointed in the US and Europe,' Bloomberg Konstantin Makienko, analysts at Moscow-based think tank Center for Analysis and Technology, as saying. 'But until the advance is paid and the assembly begins, we can't be sure of anything.'

The Turkish official cited in Bloomberg's report said technology transfer was a key factor in the decision.

'There are a lot of different levels of technology transfer,' and any offer to Turkey would probably be limited in terms of sophistication, said Makienko, the Moscow-based analyst. 'For Turkey to be able to copy the S-400 system, it would have to spend billions to create a whole new industry.'

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